FDR:
I'm curious, why can't a slow rotation be a contributing factor of bad performance?
Especially with 4 engines and a limited amount of excess thrust.
Before rotation, lift induced drag is at a minimum but you have rolling friction.
After rotation rolling friction is eliminated.
So during rotation you have more drag, isn't that fair to say?
If you combine that with very limited excess thrust, wouldn't the acceleration be minimal during rotation?
So i could imagine that during rotation the aircraft isn't able to accelerate beyond a certain speed, or at least not effectively.
Thus you wouldn't gain almost any energy during rotation.
Maybe for thrust to be that limiting, it's already well below what is required, i don't know.
A very detailed graph of speed and acceleration during takeoff would sure be interesting.